Improvement in rubber erasers



UNIT-nn STATES PATENT OFFICE.

WILLIAM N. BARTHOLOMEW, OE NEWTON CENTRE, MASSACHUSETTS, ASSIGNOR TO JOSEPH RECKENDORFER, OF NEW YORK CITY.

IMPROVEMENT IN RUBBER ERAsERs.

Specilication forming part of Letters Patent No. 84.985, dated December 15, 1868.

To all whom 'it may concern:

Be it known that I, WILLIAM N. BARIIIOL- OIWIEW, of Newton Centre, in the county of Middlesex, in the State of Massachusetts, have invented certain new and useful Improvements in Rubber Erasers; and I do hereby declare that the following is a full and exact description thereof.

My invention consists in forming the erasers with acute angles, so that they can be more successfully used than when otherwise formed to erase pencil and other marks between nearly contiguous marks and lines which are to be preserved unimpaired by contact with the eraser.

Heretofore the form of erasers has been uniformly rectangular, being such as to prevent the operator, making erasures near or between nearly contiguous marks or lines, from conveniently and distinctly seeing the point or line to be erased, and the use of which constantly wearing away and bluntin g the edge of the angle of the eraser soon renders it quite unfit for such purposes.

I make my erasers with acute angles, thereby remedyin g the defects above enumerated.

The accompanying drawings form a part. of this specification. By their aid I will describe what I consider the most convenient means of carrying out my invention.

Figure 1 is a face view, and Fig. 2 an edge view, of one form of my improved eraser. Fig. 3 is a face view, and Fig. 4 an edge view, of another form. Fig. 5 is a perspective view of the eraser at work, showing one of the positions in which it is particularly advantageous.

Similar letters of reference indicate correspondingparts in all the figures.

To produce my improved erasers, I take a broad sheet of soft vulcanized rubber, of the proper composition to form a proper eraser, and cut it, by awet knife and a straight-edge, into diamond shapes, as shown in Fig. l, instead of the right-angle forms usually produced. These diamondshaped erasers present acute angles at a and c, and obtuse angles at b and d.

In practice, that portion of the rubber adjoining the acute angles is mostly used. When it is desired to erase a large mass of words or figures, the whole of the edge or plane between one of the acute angles and either of the adjoining obtuse angles may be employed; but when erasing in narrow spaces, the rubber is slightly tilted or raised, so as to bring that portion only of the bottom plane which is in the immediate vicinity of the apex a or o in contact with the line to be erased, and in this way the points or edges a c are always kept sharp, although the angle of inclination of the planes may be slightly changed.

By reference to Fig. 5in the accompanying drawings, it will be seen that in erasing aline the form of the eraser is such that the operator can always, without change of position,

see the exact point of contact of the eraser with the said line. It will also be seen that the wear of the eraser, incident to its use, will, while it gradually alters the planes of the angles with reference to each other, instead of blunting the edge, as is the case with the rectangular form, keep it constantly sharp, and as fit for use as in the first instance. The acute angles, therefore, constitute a new and highly useful improvement in erasers, being such that the parts to be erased are more readily seen; that the edges of the eraser, by the very use for which it is designed, are kept sharper, and erasures maybe made with less liability to impair other lines or contiguous parts of a drawing than heretofore.

Some of the advantages due to my invention may be realized by molding the rubber in the form represented; but I greatly prefer to out it, as above described, from a previously-prepared sheet. Manufactured in molds, it has a hard and glossy coating, which must either be cut, or scraped, or worn away before it can be used without smutting the drawing. By vulcanizing the rubber in the sheet, and

'then cutting it as described, this evil is avoided, and the eraser is ready for use at once in its best condition. v

What I claim as new, and desire to secure by Letters Patent, isas follows: y

I claim rubber erasers made with acute angles, substantially as and for the purposes herein set forth.

JOHN L. THORNDIKE, l WILLARD O. VAN DERLIP.

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